Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Feb 4th, 2020–Feb 5th, 2020

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Northwest Coastal.

Human triggered avalanche remain likely in the wake of a heavy storm.

Confidence

High - The number, quality, or consistency of field observations is good, and supports our confidence.

Weather Forecast

TUESDAY NIGHT: Another frontal system passes through the region with 15-20 cm of snow, strong wind from the west and freezing level climbing to 1000 m.

WEDNESDAY NIGHT: Easing flurries as the front leaves the region mid-morning and another 5 cm of snow throughout the day, moderate wind from the west, freezing level drops to 700 m and alpine temperatures around -3 C.

THURSDAY: Cloudy with isolated flurries, 5-10 cm of new snow, light wind from the southwest, alpine high temperatures around -5 C.

FRIDAY: Mix of sun and cloud, light wind, alpine high temperatures around -8 C.

Avalanche Summary

Storms over the past week resulted in several cycles of natural avalanche activity. Over the weekend there were reports of large (size 2-3) storm slab avalanches and Tuesday's storm is likely causing similar activity. While most of the activity has been storm slabs releasing in the new snow, there have been a few isolated instances of avalanches failing on deeper weak layers with crown fractures up to a metre deep. A few smaller (size 1) skier triggered soft slabs were reported on Monday.

Natural avalanche activity will likely decrease in the next few days as the stormy weather eases, but storm slabs will remain sensitive to human triggering.

Snowpack Summary

A second frontal system will bring another 15-20 cm of new snow on Tuesday night bringing two day storm totals to 30-50 cm. At higher elevations moderate to strong wind will formed extra deep deposits, while lower elevations will settle rapidly due to mild temperatures and wet snow overnight.

100-150 cm of snow from the second half of January overlies a thin layer of facets that formed during the mid-January cold snap. Recent avalanche activity in the Bear Pass area and snowpack tests around Shames indicate this layer remains a concern.

A crust from mid November exists at the base of the snowpack. So far, we have only one observation from Saturday in the far north of the region showing this layer waking up during the storm. Previously, the last avalanche reported on this layer was on January 17. Potential still exists for large avalanches in surface layers to step down to this layer.

Terrain and Travel

  • Minimize exposure during periods of heavy loading from new snow and wind.
  • Storm slabs in motion may step down to deeply buried weak layers resulting in very large avalanches.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.